Wireless communication method using enhanced distributed channel access, and wireless communication terminal using same

ABSTRACT

Provided is a wireless communication terminal that communicates wirelessly. The wireless communication terminal includes a transceiver and a processor for processing a radio signal received through the transceiver or a radio signal to be transmitted through the transceiver. The processor accesses a channel according to according to a priority of data to be transmitted to the base communication terminal by the wireless communication terminal.

TECHNICAL FIELD

The present invention relates to wireless communication method and awireless communication terminal using enhanced distributed channelaccess.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel Therefore, required is a technology capable of efficiently usingbandwidths by simultaneously transmitting data between a plurality ofterminals and base terminals.

DISCLOSURE Technical Problem

An object of an embodiment of the present invention is to provide awireless communication terminal using enhanced distributed channelaccess.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal that wirelessly communicates with a base wirelesscommunication terminal includes: a transceiver; and a processor forprocessing a radio signal received through the transceiver or a radiosignal to be transmitted through the transceiver. The processor isconfigured to access a channel according to a priority of data to betransmitted to the base communication terminal by the wirelesscommunication terminal.

The processor may be configured to switch a parameter set, which is aset of parameters used for the channel access, from a first parameterset to a second parameter set based on whether the base wirelesscommunication terminal triggers a multi-user uplink transmissionparticipation of the wireless communication terminal.

The processor may be configured to transmit the trigger-based physicallayer protocol data unit (PPDU) to the base wireless communicationterminal using the transceiver, set a second parameter set timeraccording to an immediate response reception based on whether animmediate response to a MAC protocol data unit (MPDU) included in thetrigger-based PPDU is received, and when the second parameter set timerexpires, terminate the application of the second parameter set.

The processor may be configured to set the second parameter set timerwhen the immediate response reception ends.

The processor may be configured to set the second parameter set timerfor an access category of an MPDU for which the immediate response isreceived.

The processor may be configured to determine when to set the secondparameter set timer based on a type of responding requested by the MPDUincluded in the trigger-based PPDU.

When the MPDU included in the trigger-based PPDU does not request anACK, the processor may be configured to set the second parameter settimer when the transmission of the trigger-based PPDU ends.

The MPDU included in the trigger-based PPDU may be a QoS data frame.

The processor may be configured to receive a beacon frame from the basewireless communication terminal and obtain information indicating aperiod of the second parameter set timer from the beacon frame.

When switching the parameter set from the first parameter set to thesecond parameter set, the processor may be configured to set the secondparameter set timer.

The processor may be configured to calculate a random integer value in acontention window (CW), set a backoff timer based on the random integervalue, and access a channel based on the back off timer and apredetermined slot time, wherein the parameter set may include a minimumvalue (CWmin) of the CW and a maximum value (CWmax) of the CW.

The processor may be configured to calculate a random integer value in acontention window (CW), set a backoff timer based on the random integervalue, access a channel based on the back off timer and a predeterminedslot time, and when a value of the CW is greater than the maximum value(CWmax) of the CW according to a priority of the traffic, set the valueof the CW to the CWmax.

The processor may be configured to operate a plurality of queues thatare classified according to an access category of data stored in a queueand perform a backoff procedure of accessing a channel based on a timecorresponding to a backoff timer in each of the plurality of queues, andwhen there is no data stored in the queue and the backoff timercorresponding to the queue is 0, perform no operation at a slot boundaryof the backoff timer, wherein the backoff timer may be set based on arandom integer value calculated within a contention window (CW), and maybe reduced when the channel is idle for a predetermined slot time.

When there is no data stored in the queue and the backoff timercorresponding to the queue is 0, the processor may be configured tomaintain the backoff timer to be 0.

According to an embodiment of the present invention, an operation methodof a wireless communication terminal that wirelessly communicates with abase wireless communication terminal includes: accessing a channelaccording to a priority of data to be transmitted to the base wirelesscommunication terminal; and transmitting the data through the channel.

The accessing of the channel may include: switching a parameter set,which is a set of parameters used for the channel access, from a firstparameter set to a second parameter set based on whether the basewireless communication terminal triggers a multi-user uplinktransmission participation of the wireless communication terminal; andaccessing a channel using a second set of parameters based on a priorityof the traffic to be transmitted to the base communication terminal bythe wireless communication terminal.

The method may further include transmitting a trigger-based PPDU to thebase wireless communication terminal using the transceiver, wherein theswitching from the first parameter set to the second parameter set mayinclude: setting a second parameter set timer according to an immediateresponse reception based on whether an immediate response to a MACprotocol data unit (MPDU) included in the trigger-based PPDU isreceived, and when the second parameter set timer expires, terminatingthe application of the second parameter set.

The setting of the second parameter set timer may include setting thesecond parameter set timer when the immediate response reception ends.

The setting of the second parameter set timer may include setting thesecond parameter set timer for an access category of an MPDU for whichthe immediate response is received.

The setting of the second parameter set timer may determine when to setthe second parameter set timer based on a type of responding requestedby the MPDU included in the trigger-based PPDU.

The setting of the second parameter set timer may include setting thesecond parameter set timer when transmission of the trigger based PPDUends when the MPDU included in the trigger based PPDU does not requestan ACK.

Advantageous Effects

An embodiment of the present invention provides a wireless communicationmethod using enhanced distributed channel access and a wirelesscommunication terminal using the same.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless LAN system according to an embodiment of thepresent invention.

FIG. 2 shows a wireless LAN system according to another embodiment ofthe present invention.

FIG. 3 shows a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 shows a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 shows a process that a station sets an access point and a linkaccording to an embodiment of the present invention.

FIG. 6 shows that a wireless communication terminal according to anembodiment of the present invention adjusts EDCA parameters according toUL MU transmission.

FIG. 7 shows a method of applying an MU EDCA parameter set by a wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 8 shows a method of aggregating multi-TID A-MPDUs by a wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 9 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention receives informationon an MU EDCA parameter set from a base wireless communication terminaland applies the information on an MU EDCA parameter set.

FIG. 10 describes an operation in which a base wireless communicationterminal according to an embodiment of the present invention transmits aBSR through a QoS Control field.

FIG. 11 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention receivesinformation on an MU EDCA parameter set from a base wirelesscommunication terminal and applies the information on an MU EDCAparameter set.

FIG. 12 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention obtainsinformation on an MU EDCA parameter set from a trigger frame and appliesthe information on an MU EDCA parameter set.

FIG. 13 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention obtainsinformation on an MU EDCA parameter set from a target wake time elementand applies the information on an MU EDCA parameter set.

FIG. 14 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention terminates the MUEDCA parameter application.

FIG. 15 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention terminates theMU EDCA parameter application.

FIG. 16 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention applies an MUEDCA parameter.

FIG. 17 shows an A-MPDU generated by a wireless communication terminalaccording to an embodiment of the present invention and a type ofresponding for a corresponding A-MPDU.

FIG. 18 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention applies an MUEDCA parameter.

FIG. 19 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention applies an MU EDCAparameter set.

FIG. 20 shows an operation of changing a CW value while a wirelesscommunication terminal according to an embodiment of the presentinvention changes an EDCA parameter set.

FIG. 21 shows an operation of changing a CW value while a wirelesscommunication terminal according to an embodiment of the presentinvention changes an EDCA parameter set.

FIG. 22 shows a specific format of an MU EDCA parameter set elementaccording to an embodiment of the present invention.

FIG. 23 shows a specific format of an MU EDCA parameter set elementaccording to another embodiment of the present invention.

FIG. 24 shows an EDCA operation after UL MU transmission of a wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 25 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according to theembodiment of the present invention is empty and the backoff timer is 0.

FIG. 26 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according toanother embodiment of the present invention is empty and the backofftimer is 0.

FIG. 27 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according toanother embodiment of the present invention is empty and the backofftimer is 0.

FIG. 28 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2016-0114822 (2016 Sep. 7), Nos. 10-2016-0116877(2016 Sep. 10), Nos. 10-2016-0116965 (2016 Sep. 12), Nos.10-2016-0117898 (2016 Sep. 13), Nos. 10-2016-0122488 (2016 Sep. 23),Nos. 10-2016-0147189 (2016 Nov. 6), and Nos. 10-2017-0022227 (2017 Feb.20) filed in the Korean Intellectual Property Office and the embodimentsand mentioned items described in the respective applications areincluded in the Detailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STA5, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

In a specific embodiment, the AP 200 may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in an independent network, such as an ad-hoc network, whichis not connected to an external distribution service. In addition, theAP 200 may be at least one of a base station, an eNB, and a transmissionpoint TP. The AP 200 may also be referred to as a base wirelesscommunication terminal.

In a frequency band commonly used by various wireless communicationdevices, such as an unlicensed band, a wireless communication terminalmay access the channel through a contention procedure. Specifically, ifthe channel to be accessed by the wireless communication terminal isidle for a predetermined time, the wireless communication terminalstarts the backoff procedure. In the backoff procedure, the wirelesscommunication terminal obtains a random integer value in a contentionwindow (CW) and sets the random integer value as a backoff timer. If thecorresponding channel is idle during a predetermined slot time, thewireless communication terminal decreases the backoff timer. If thevalue of the backoff timer is 0, the wireless communication terminalaccesses the corresponding channel. At this time, if the correspondingchannel is busy, the wireless communication terminal stops the backoffprocedure. If the channel to be accessed by the wireless communicationterminal is idle for a predetermined time, the wireless communicationterminal resumes the backoff procedure again.

Further, the wireless communication terminal may access the channelaccording to the priority of the data to be transmitted. Specifically,the wireless communication terminal may use the CW determined accordingto the priority of the data to be transmitted. At this time, the minimumvalue CWmin and the maximum value CWmax of CW are determined accordingto the priority of data to be transmitted by the wireless communicationterminal. In addition, the predetermined time at which the wirelesscommunication terminal waits to start the backoff procedure isdetermined according to the priority of the data to be transmitted bythe wireless communication terminal. Also, the wireless communicationterminal may wait for a designated time according to the priority of thedata to be transmitted, and then start the backoff procedure. Thedesignated time according to the priority is referred to as arbitrationinterframe space (AIFS). This operation is referred to as enhanceddistributed channel access (EDCA). In addition, the priority of data maybe determined according to an access category (AC).

The base wireless communication terminal may trigger uplink transmissionof one or more wireless communication terminals to the base wirelesscommunication terminal. At this time, one or more wireless communicationterminals may perform uplink transmission to a base wirelesscommunication terminal using Orthogonal Frequency-Division MultipleAccess (OFDMA). Further, the base wireless communication terminaltransmits trigger information to one or more wireless communicationterminals through a trigger frame or a MAC header to trigger uplinktransmissions for the base wireless communication terminal of one ormore wireless communication terminals. At this time, the base wirelesscommunication terminal accesses the channel for uplink transmission ofone or more wireless communication terminals. In addition, one or morewireless communication terminals access the channel for uplinktransmission of each of the one or more wireless communicationterminals. Therefore, when the uplink transmission of one or morewireless communication terminals is scheduled for uplink transmission bythe base wireless communication terminal, the uplink transmission of oneor more wireless communication terminals has a higher priority thantransmission of other wireless communication terminals that transmitdata having the same priority. In addition, since the base wirelesscommunication terminal and one or more wireless communication terminalssimultaneously access the channel for the same transmission, the channelaccess efficiency may decrease. Therefore, when the uplink multi-user(UL-MU) transmission is scheduled, it is necessary to adjust the EDCAparameter value.

In a frequency band commonly used by various wireless communicationdevices, such as an unlicensed band, a wireless communication terminalmay access the channel through a contention procedure. Specifically, ifthe channel to be accessed by the wireless communication terminal isidle for a predetermined time, the wireless communication terminalstarts the backoff procedure. In the backoff procedure, the wirelesscommunication terminal obtains a random integer value within acontention window (CW) and sets the random integer value as a backofftimer. When the corresponding channel is idle during a predeterminedslot time, the wireless communication terminal decreases the backofftimer. When the value of the backoff timer is 0, the wirelesscommunication terminal accesses the corresponding channel. At this time,when the corresponding channel is busy, the wireless communicationterminal stops the backoff procedure. When the channel to be accessed bythe wireless communication terminal is idle for a predetermined time,the wireless communication terminal resumes the backoff procedure again.

Further, the wireless communication terminal may access the channelaccording to the priority of the data to be transmitted. Specifically,the wireless communication terminal may use the CW determined accordingto the priority of the data to be transmitted. At this time, the minimumvalue CWmin and the maximum value CWmax of CW are determined accordingto the priority of data to be transmitted by the wireless communicationterminal. In addition, the predetermined time at which the wirelesscommunication terminal waits to start the backoff procedure isdetermined according to the priority of the data to be transmitted bythe wireless communication terminal. Also, the wireless communicationterminal may wait for a designated time according to the priority of thedata to be transmitted, and then start the backoff procedure. Thedesignated time according to the priority is referred to as arbitrationinterframe space (AIFS). This operation is referred to as enhanceddistributed channel access (EDCA). In addition, the priority of data maybe determined according to an access category (AC).

The base wireless communication terminal may trigger uplink transmissionof one or more wireless communication terminals to the base wirelesscommunication terminal. At this time, one or more wireless communicationterminals may perform uplink transmission to a base wirelesscommunication terminal using Orthogonal Frequency-Division MultipleAccess (OFDMA). Further, the base wireless communication terminaltransmits trigger information to one or more wireless communicationterminals through a trigger frame or a MAC header to trigger uplinktransmissions for the base wireless communication terminal of one ormore wireless communication terminals. At this time, the base wirelesscommunication terminal accesses the channel for uplink transmission ofone or more wireless communication terminals. In addition, one or morewireless communication terminals access the channel for uplinktransmission of each of the one or more wireless communicationterminals. Therefore, when the uplink transmission of one or morewireless communication terminals is scheduled for uplink transmission bythe base wireless communication terminal, the uplink transmission of oneor more wireless communication terminals has a higher priority thantransmission of other wireless communication terminals that transmitdata having the same priority. In addition, since the base wirelesscommunication terminal and one or more wireless communication terminalssimultaneously access the channel for the same transmission, the channelaccess efficiency may decrease. Therefore, when the uplink multi-user(UL-MU) transmission is scheduled, it is necessary to adjust the EDCAparameter value.

FIG. 6 shows that a wireless communication terminal according to anembodiment of the present invention adjusts EDCA parameters according toUL MU transmission.

A wireless communication terminal that is scheduled for UL MUtransmission may use a channel access method to ensure channel accesssuccess with a lower probability than when it is not scheduled for UL MUtransmission. Specifically, a wireless communication terminal scheduledfor UL MU transmission may use a separate EDCA parameter set. In aspecific embodiment, a wireless communication terminal scheduled for ULMU transmission may use an EDCA parameter set that attempts to accessthe channel with a lower probability than the previously used EDCAparameter set in channel access for transmitting the same data. At thistime, the EDCA parameter set is a set of parameters used in the EDCAoperation according to the priority of the data transmitted by thewireless communication terminal. Specifically, the EDCA parameter setmay include parameters for CW. At this time, the parameter for CW mayinclude at least one of CWmin and CWmax. In addition, the EDCA parameterset may include a parameter value related to a predetermined time atwhich the wireless communication terminal waits to start the backoffprocedure. At this time, the predetermined time may be the AIFSdescribed above. For convenience of description, a separate EDCAparameter set used by a wireless communication terminal scheduled for ULMU transmission is referred to as an MU EDCA parameter set.

As in the embodiment of FIG. 7, the wireless communication terminal towhich the MU EDCA parameter set is applied accesses the channel when thechannel to be accessed is idle for a longer AIFS period than the generalAIFS period waiting for transmission of the corresponding data. When thecorresponding channel is idle during the AIFS corresponding to the MUEDCA parameter set, the wireless communication terminal starts a backoffprocedure for the corresponding channel.

The base wireless communication terminal may transmit information on theMU EDCA parameter set to the wireless communication terminals scheduledfor UL MU transmission. Specifically, the base wireless communicationterminal may transmit an MU EDCA parameter element including informationon the MU EDCA parameter set to a wireless communication terminalscheduled for UL MU transmission. At this time, the base wirelesscommunication terminal may transmit the MU EDCA parameter element usingthe beacon frame. A concrete method of switching the EDCA parameter setwill be described in detail with reference to FIG. 7 to FIG. 11.

FIG. 7 shows a method of applying an MU EDCA parameter set by a wirelesscommunication terminal according to an embodiment of the presentinvention.

The wireless communication terminal may determine whether to apply theMU EDCA parameter set by each AC. Specifically, the wirelesscommunication terminal may determine whether to apply the MU EDCAparameter set by each AC based on UL MU transmission. In a specificembodiment, the wireless communication terminal may apply the MU EDCAparameter set to data transmission corresponding to the AC scheduled forUL MU transmission. This is because if the MU EDCA parameter set isapplied to an AC that does not correspond to the UL MU transmissiontarget, the channel access fairness may be degraded.

In the embodiment of FIG. 7, the wireless communication terminal appliesthe MU EDCA parameter set. At this time, the wireless communicationterminal applies the MU EDCA parameter set to some AC (e.g., BE and BK)indicated by the MU EDCA parameter set. Therefore, in order for AC totransmit traffic corresponding to BE and BK, the wireless communicationterminal uses the MU EDCA parameter set to access the channel. At thistime, the probability that the wireless communication terminal may starttransmission within a predetermined time is lower than when a generalEDCA parameter set is used.

When the wireless communication terminal determines whether to apply theMU EDCA parameter set for each AC, the wireless communication terminalmay guide the AC to which the MU EDCA parameter set is applied to aspecific AC to degrade the fairness with other terminals. For example,the wireless communication terminal may induce only the data of the AChaving a relatively large backoff timer value to be scheduled for the ULMU transmission. Therefore, the wireless communication terminal maydetermine whether to apply the MU EDCA parameter set based on thecurrent channel access wait state. Specifically, when the wirelesscommunication terminal applies the MU EDCA parameter set, the wirelesscommunication terminal may be regulated to mandatorily apply the MU EDCAparameter set to the primary AC with the shortest channel access waittime. At this time, the channel access wait time may be determined basedon the value of the remaining backoff timer and the AIFS value.Specifically, the channel access wait time may be the sum of the timecorresponding to the backoff timer and the AIFS. When there are aplurality of wireless communication terminals having a minimum channelaccess wait time, the wireless communication terminal may restrict theEDCA parameter set application condition to mandatorily apply the MUEDCA parameter set to a plurality of ACs.

FIG. 8 shows a method of aggregating multi-TID A-MPDUs by a wirelesscommunication terminal according to an embodiment of the presentinvention.

The wireless communication terminal may aggregate a plurality of MPDUscorresponding to each of a plurality of TIDs and generate anAggregate-MAC Protocol Data Unit (A-MPDU). At this time, the A-MPDU maybe referred to as a multi-TID A-MPDU. At this time, when the wirelesscommunication terminal intentionally inserts the MPDU of the TIDcorresponding to the AC having the largest channel access wait time intothe multi-TID A-MPDU, the transmission fairness between the wirelesscommunication terminals may be lowered. Therefore, the wirelesscommunication terminal may be restricted to transmit the multi-TIDA-MPDU including the MPDU of the TID corresponding to the AC having thesmallest channel access wait time. At this time, the size of the MPDU ofthe TID corresponding to the AC having the smallest channel access waittime included in the multi-TID A-MPDU may be larger than a predeterminedsize. In addition, when the wireless communication terminal performs theUL MU transmission, the wireless communication terminal may berestricted to transmit the multi-TID A-MPDU, including the TID indicatedby the base wireless communication terminal.

The AC having the smallest channel access wait time in the wirelesscommunication terminal of FIG. 8 is VO. The wireless communicationterminal generates the multi-TID A-MDPU, including the MPDU of the TIDTID1 corresponding to the VO. The wireless communication terminaltransmits the generated multi-TID A-MPDU to the base wirelesscommunication terminal. At this time, the wireless communicationterminal may transmit a buffer status report (BSR) through the QoScontrol field of the MPDU included in the multi-TID A-MPDU. This will bedescribed in more detail with reference to FIG. 10. The wirelesscommunication terminal may maintain channel access fairness with otherwireless communication terminals through these embodiments.

As described above, the base wireless communication terminal maytransmit information on the MU EDCA parameter set to the wirelesscommunication terminal. This will be described with reference to FIGS. 9to 11.

FIG. 9 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention receives informationon an MU EDCA parameter set from a base wireless communication terminaland applies the information on an MU EDCA parameter set.

When the wireless communication terminal transmits the BSR, the wirelesscommunication terminal may apply the MU EDCA parameter set.Specifically, when the wireless communication terminal transmits theBSR, the wireless communication terminal may apply the MU EDCA parameterset to the AC related to the BSR transmission. The AC related to the BSRtransmission may be an AC with a buffer state reported through the BSR.In addition, when the wireless communication terminal transmits the BSR,the wireless communication terminal may apply the MU EDCA parameter setto all ACs. This is because the base wireless communication terminal mayschedule UL MU transmission based on the BSR transmitted by the wirelesscommunication terminal. Specifically, the wireless communicationterminal may access the channel by applying the MU EDCA parameter setfrom when the transmission of the BSR is completed, as in the embodimentof FIG. 9(a). The wireless communication terminal may transmit the BSRto the base wireless communication terminal using various methods. Thiswill be described with reference to FIG. 10.

FIG. 10 describes an operation in which a base wireless communicationterminal according to an embodiment of the present invention transmits aBSR through a QoS Control field.

The wireless communication terminal may transmit the BSR using the QoScontrol field of the MAC header. In addition, the format of the BAcontrol field may be the same as that of the embodiment of FIG. 10(a).Specifically, the wireless communication terminal may transmit the BSRusing the QoS control field of the MPDU while transmitting the MPDUincluding the QoS data. In addition, the wireless communication terminalmay transmit the BSR using the QoS control field of the MPDU whiletransmitting the QoS null MPDU that does not include data. Also, thewireless communication terminal may insert a QoS Null MPDU into theA-MPDU regardless of the TID number limitation that the multi-TID A-MPDUmay include.

In the uplink single user (UL SU) transmission as in the embodiment ofFIG. 10(b), the wireless communication terminal may transmit the BSRusing the QoS control field. Further, in the UL MU transmissiontriggered by the trigger frame, the wireless communication terminal maytransmit the BSR using the QoS control field. In addition, the wirelesscommunication terminal receives the A-MPDU from the base wirelesscommunication terminal, and the wireless communication terminal maytransmit the BSR using the QoS control field while transmitting the BAframe for the A-MPDU. In addition, the wireless communication terminalmay receive the BSRP, which is a trigger frame for triggering the BSRtransmission, and the wireless communication terminal may transmit theBSR using the QoS control field of the QoS Null MPDU.

Again, FIG. 9 is described. In another specific embodiment, the wirelesscommunication terminal may apply the MU EDCA parameter set whenreceiving the information on UL MU scheduling from the base wirelesscommunication terminal. At this time, the information on the UL MUscheduling may be information indicating that the UL MU transmission isscheduled. In addition, the base wireless communication terminal maytransmit information on UL MU transmission scheduling to the wirelesscommunication terminal using at least one of a beacon frame and anaction frame. The wireless communication terminal may obtain informationon UL MU transmission scheduling from at least one of a beacon frame andan action frame. In this case, the Action frame may be an Action no ACKframe not requiring an ACK frame for the Action frame. Specifically, thewireless communication terminal receives information on the UL MUscheduling from the base wireless communication terminal, and appliesthe MU EDCA parameter set to the AC indicated by the UL MU schedulinginformation. In addition, the wireless communication terminal may applythe MU EDCA parameter set to the AC having the history of transmittingthe BSR within a predetermined period from when receiving theinformation on the UL MU scheduling. Information on the UL MU schedulingmay be included in the reserved bits of the HE operation element. Also,if the beacon frame includes an MU EDCA parameter set, the beacon frameimplicitly indicates that the UL MU transmission is scheduled. Inaddition, a field indicating the MU EDCA parameter set may include afield indicating that the UL MU transmission is scheduled. In theembodiment of FIG. 9(b), the wireless communication terminal receives abeacon frame. The wireless communication terminal obtains information onUL MU scheduling from the beacon frame. At this time, the wirelesscommunication terminal applies the MU EDCA parameter set to the AC forwhich the BSR is transmitted within a period from the reference point tothe time when the UL MU scheduling information is received.

In another specific embodiment, the base wireless communication terminalmay transmit specific UL MU transmission scheduling information inaddition to whether UL MU transmission is scheduled. This will bedescribed with reference to FIG. 11.

FIG. 11 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention receivesinformation on an MU EDCA parameter set from a base wirelesscommunication terminal and applies the information on an MU EDCAparameter set.

The base wireless communication terminal may transmit information foridentifying the wireless communication terminal for which the UL MUtransmission is scheduled. The wireless communication terminal mayreceive information for identifying the wireless communication terminalscheduled for the UL MU transmission and apply the MU EDCA parameter setbased on the information for identifying the wireless communicationterminal for which the UL MU transmission is scheduled. Specifically,the base wireless communication terminal may periodically transmitinformation for identifying a wireless communication terminal scheduledfor the UL MU transmission for a predetermined period. At this time, thebase wireless communication terminal may transmit information foridentifying a wireless communication terminal scheduled for UL MUtransmission for a predetermined period using a beacon frame. Also, thebase wireless communication terminal may transmit information foridentifying a wireless communication terminal scheduled for UL MUtransmission using the TIM element of the beacon frame. In anotherspecific embodiment, the base wireless communication terminal maytransmit information for identifying the wireless communication terminalscheduled for the UL MU transmission using an element indicatinginformation related to UL MU scheduling. In addition, the base wirelesscommunication terminal may transmit not only the information foridentifying the wireless communication terminal scheduled for the UL MUtransmission, but also the information for indicating the AC of the ULMU transmission scheduled data. At this time, the information indicatingthe AC of the UL MU transmission scheduled data may indicate all ACs insome cases. In addition, the base wireless communication terminal maytransmit not only the information for identifying the wirelesscommunication terminal scheduled for the UL MU transmission, but alsoinformation indicating the time point at which the UL MU transmission istriggered. At this time, the time point at which the UL MU transmissionis triggered may indicate the time point at which the triggerinformation is transmitted. Specifically, the trigger information mayinclude a trigger frame. In addition, the base wireless communicationterminal may transmit the backoff timer value of the backoff procedurefor transmitting the trigger information.

In the embodiment of FIG. 11, the first station STA1 transmits a BSR toan access point AP. The access point AP receives the BSR and schedulesthe uplink transmission of the first station STA1 based on the receivedBSR. The access point AP transmits information on the scheduled UL MUtransmission using a beacon frame. At this time, the information on thescheduled UL MU transmission may include information for identifying thewireless communication terminal scheduled for the UL MU transmission. Atthis time, the information on the scheduled UL MU transmission may be abit map indicating whether the Association ID (AID) or the wirelesscommunication terminal corresponding to the AID is scheduled for the ULMU transmission. The first station STA1 receives the beacon frame fromthe access point AP and obtains information on the scheduled UL MUtransmission from the beacon frame. When the information on thescheduled UL MU transmission indicates that the first station STA1 isscheduled for UL MU transmission, the first station STA1 applies the MUEDCA parameter set.

FIG. 12 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention obtainsinformation on an MU EDCA parameter set from a trigger frame and appliesthe information on an MU EDCA parameter set.

The wireless communication terminal may apply the MU EDCA parameter setbased on whether the trigger information received by the wirelesscommunication terminal triggers the multi-user uplink transmission ofthe wireless communication terminal. Specifically, based on whether theUser Info field of the trigger frame received by the wirelesscommunication terminal indicates the wireless communication terminal,the wireless communication terminal may apply the MU EDCA parameter set.In a specific embodiment, the wireless communication terminal may applythe MU EDCA parameter set when receiving the trigger frame. In thisembodiment, in order for the wireless communication terminal to applythe MU EDCA parameter, the base wireless communication terminal does nottransmit any additional information. However, the base wirelesscommunication terminal attempts channel access for transmitting thetrigger frame, and the wireless communication terminal scheduled for ULMU transmission at this time may also attempt channel access using theexisting EDCA parameter set.

Therefore, the base wireless communication terminal may transmitinformation on the wireless communication terminal triggered aftertransmitting trigger information using trigger information.Specifically, the base wireless communication terminal may transmitinformation on a wireless communication terminal to be triggered after atrigger frame is transmitted using the User Info field of the triggerframe. In a specific embodiment, when the field indicating the resourceunit (RU) allocation information included in the User Info fieldindicates a predetermined value, the User Info field may indicate thatthe wireless communication terminal indicated by the corresponding UserInfo field is to be triggered after the trigger frame is transmitted. Atthis time, when the RU assignment information indicated by the User Infofield is a predetermined value, the wireless communication terminal mayapply the MU EDCA parameter set indicated by the corresponding User Infofield. In another specific embodiment, if the value of the fieldindicating the RU allocation information included in the User Info fieldis a predetermined value, the field indicating the RU allocationinformation may indicate an AC to which the MU EDCA parameter set isapplied.

In these embodiments, the wireless communication terminal indicated bythe User Info field may ignore the remaining fields except the fieldindicating the RU allocation information and the field indicating thewireless communication terminal indicated by the User Info field in theUser Info field. In addition, the size of the User Info field indicatingthe information on the wireless communication terminal to be triggeredafter the transmission of the trigger frame may be smaller than the sizeof the general User Info field. Specifically, the base wirelesscommunication terminal may transmit the User Info field while omittingat least one of the fields indicating the RU allocation information ofthe User Info field and the fields other than the field indicating thewireless communication terminal indicated by the User Info field. A UserInfo field indicating information on a wireless communication terminalto be triggered after the transmission of the trigger frame may indicateinformation on a plurality of wireless communication terminals to betriggered after the transmission of the trigger frame. At this time, theUser Info field may include a group AID. In another specific embodiment,the User Info field may include a broadcast AID.

In the embodiment of FIG. 12(a), the base wireless communicationterminal transmits a trigger frame to the wireless communicationterminal. The wireless communication terminal indicated by the triggerframe applies the MU EDCA parameter set. At this time, the trigger framemay include information on the wireless communication terminal to betriggered after the trigger frame is transmitted as described above.Specifically, the format of the trigger frame may be the same as thatshown in FIG. 12(b).

The base wireless communication terminal transmits a target wake time(TWT) element to signal to the wireless communication terminal a time atwhich the wireless communication terminal should wake up. Specifically,the base wireless communication terminal may transmit a TWT elementusing a beacon frame. When the base wireless communication terminalattempts channel access to transmit a trigger frame in a service periodindicated by a TWT element, a wireless communication terminal triggeredby the trigger frame may attempt channel access for uplink transmission.In this situation, the channel access attempt of the wirelesscommunication terminal may lower the chance of the channel accesssuccess of the base wireless communication terminal. Therefore, thewireless communication terminal may apply the MU EDCA parameter setbased on the TWT element. This will be described in more detail withreference to FIG. 13.

FIG. 13 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention obtainsinformation on an MU EDCA parameter set from a target wake time elementand applies the information on an MU EDCA parameter set.

The wireless communication terminal may apply the MU EDCA parameter setbased on the TWT element. Specifically, the wireless communicationterminal may apply the MU EDCA parameter set based on the service periodindicated by the TWT element. At this time, the service periodrepresents a period that the wireless communication terminal previouslyagrees to exchange frames with the base wireless communication terminal.In a specific embodiment, the wireless communication terminal may applythe MU EDCA parameter set from a time preceding by a predetermined timefrom the start time point of the service period indicated by the TWTelement. At this time, the predetermined time may be signaled by thebase wireless communication terminal. Specifically, the predeterminedtime may be signaled by the base wireless communication terminal throughan element of the beacon frame. For example, the predetermined time maybe signaled by the base wireless communication terminal through the MUEDCA parameter set element. Specifically, the predetermined time may besignaled by the base wireless communication terminal through an elementof the beacon frame.

In addition, the wireless communication terminal may terminate the MUEDCA parameter set application based on the service period indicated bythe TWT element. Specifically, the wireless communication terminal maybe allowed to terminate the MU EDCA parameter set application when apredetermined time elapses from the service period indicated by the TWTelement. In a specific embodiment, the wireless communication terminalmay terminate the MU EDCA parameter set application based on the starttime point of the service period indicated by the TWT element. Forexample, the wireless communication terminal may be allowed to terminatethe MU EDCA parameter set application when a predetermined time elapsesfrom the start time point of the service period indicated by the TWTelement. In another specific embodiment, the communication terminal mayterminate the MU EDCA parameter set application based on the end timepoint of the service period indicated by the TWT element. For example,the wireless communication terminal may terminate the MU EDCA parameterset application at the end time point of the service period indicated bythe TWT element.

In the embodiment of FIG. 13, the base wireless communication terminalsignals a service period for a TWT operation by transmitting a beaconframe including a TWT element. The wireless communication terminalreceiving the beacon frame determines the MU EDCA parameter set starttime point and the end time point based on the TWT element.Specifically, the wireless communication terminal receiving the beaconframe determines the MU EDCA parameter set application start time pointbased on the start time point of the service period indicated by the TWTelement. In addition, the wireless communication terminal receiving thebeacon frame determines the MU EDCA parameter set application end timepoint based on the start time point of the service period indicated bythe TWT element. In another specific embodiment, the wirelesscommunication terminal receiving the beacon frame determines the MU EDCAparameter set application end time point based on the end time point ofthe service period indicated by the TWT element.

The MU EDCA parameter is a channel access condition that is moredisadvantageous than a typical EDCA parameter set. Therefore, thewireless communication terminal needs to terminate the MU EDCA parameterset application. The wireless communication terminal switches the MUEDCA parameter set to the normal EDCA parameter set when terminating theMU EDCA parameter application. This will be described with reference toFIGS. 14 to 15.

FIG. 14 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention terminates the MUEDCA parameter application.

If the MU EDCA parameter set application condition is not satisfieduntil a certain time elapses from when the timer is set, the wirelesscommunication terminal may set an MU EDCA timer for terminating the MUEDCA parameter set application. Specifically, the wireless communicationterminal may set the MU EDCA timer when receiving the triggerinformation. At this time, when the MU EDCA parameter set applicationcondition is not satisfied for a certain period after setting the MUEDCA timer, the wireless communication terminal may be allowed toterminate the MU EDCA parameter set application. Specifically, if the ULMU transmission of the wireless communication terminal is not scheduledfor a certain period from when the MU EDCA timer is set, the wirelesscommunication terminal may be allowed to terminate the MU EDCA parameterset application.

In another embodiment, the wireless communication terminal may set an MUEDCA timer upon receiving a response to the transmission of atrigger-based physical layer protocol data unit (PPDU) of the wirelesscommunication terminal. Specifically, when the wireless communicationterminal receives the response to the trigger-based PPDU transmission,the wireless communication terminal may set the MU EDCA timer. This isbecause if the trigger-based PPDU transmission of the wirelesscommunication terminal fails, the base wireless communication terminalmay again attempt the trigger information transmission. In thisembodiment, the wireless communication terminal may prepare for a casein which the response to the trigger-based PPDU transmission is notreceived. Specifically, when the wireless communication terminal doesnot receive a response to the trigger-based PPDU transmission from thetime when the trigger-based PPDU is transmitted until the time pointafter the predetermined time, the wireless communication terminal mayset the MU EDCA parameter set timer. At this time, the predeterminedtime may be aSIFSTime)+aRxPHYStartDelay+(2× aSlotTime).

In the embodiment of FIG. 14(a), the wireless communication terminalreceives the trigger frame TF from the base wireless communicationterminal. The wireless communication terminal transmits a trigger-basedPPDU including an MPDU corresponding to TID1 and TID3 to the basewireless communication terminal. The wireless communication terminalreceives the M-BA frame indicating the ACK for the MPDU included in thetrigger-based PPDU from the base wireless communication terminal. Inthis operation, the wireless communication terminal may set the MU EDCAtimer option1 when receiving the trigger frame TF as described above. Inaddition, the wireless communication terminal may set the MU EDCA timeroption2 when receiving the M-BA frame as described above.

In addition, when the wireless communication terminal reports as the BSRthat the buffer for the corresponding AC is empty with respect to one ormore ACs to the base wireless communication terminal, the wirelesscommunication terminal receives an ACK for transmission of data of thecorresponding AC, and terminates the MU EDCA parameter set application.In the embodiment of FIG. 14(b), the wireless communication terminalreports to the base wireless communication terminal that the buffer forTID1 is empty while transmitting the trigger-based PPDU. Therefore, whenthe wireless communication terminal receives the M-BA frame for the lasttransmission of the MPDU corresponding to TID1, the wirelesscommunication terminal converts the MU EDCA parameter set into a generalEDCA parameter set Legacy. In another embodiment, the wirelesscommunication terminal sets a first MU EDCA timer according to receptionof the trigger information, and sets the MU EDCA timer according to thereception of the response to the trigger-based PPDU transmission. Atthis time, the period of the second timer may be shorter than the periodof the first MU timer. Specifically, the wireless communication terminalmay set a first MU EDCA timer when receiving the trigger information andset an MU EDCA timer when receiving a response to the trigger-based PPDUtransmission. In the embodiment of FIG. 14(c), when the wirelesscommunication terminal receives the trigger frame TF, it sets the firstMU EDCA timer option1. Also, the wireless communication terminal sets asecond MU EDCA timer option2 that expires earlier than the expirationtime set by the first MU EDCA timer option when receiving the M-BAframe.

Further, the wireless communication terminal may set the MU EDCA timeraccording to the MU EDCA parameter application condition. This will bedescribed in detail with reference to FIG. 15.

FIG. 15 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention terminates theMU EDCA parameter application.

When the wireless communication terminal applies the MU EDCA parameter,the wireless communication terminal may set the MU EDCA timer.Specifically, when the wireless communication terminal transmits the BSRto the base wireless communication terminal, the wireless communicationterminal may apply the MU EDCA parameter set and set the MU EDCA timer.At this time, when the trigger frame received by the wirelesscommunication terminal triggers the data transmission of the AC thattransmits the BSR, the wireless communication terminal may update theexisting MU EDCA timer to the MU EDCA timer that expires later than theexpiration time of the existing MU EDCA timer. In the embodiment of FIG.15(a), the first station STA1 transmits a BSR to an access point AP. Atthis time, the first station STA1 applies the MU EDCA parameter set andsets the MU EDCA timer. The first station STA1 receives a trigger framethat triggers the traffic transmission for the AC that transmits the BSRfrom the access point AP. Accordingly, the first station STA1 updatesthe previously set MU EDCA timer to the MU EDCA timer that expires laterthan the expiration time of the previously set MU EDCA timer.

In addition, when the wireless communication terminal applies the MUEDCA parameter set based on the UL MU transmission schedulinginformation included in the beacon frame, the wireless communicationterminal may terminate the MU EDCA parameter set application based onthe UL MU transmission scheduling information. Specifically, when thebeacon frame does not include information on the UL MU transmissionscheduling, the wireless communication terminal may be allowed toterminate the MU EDCA parameter set application based on the beaconframe. Also, if the information on the UL MU transmission schedulingincluded in the beacon frame indicates that the wireless communicationterminal is not scheduled for UL MU transmission, the wirelesscommunication terminal may be allowed to terminate the MU EDCA parameterset application based on the UL MU transmission scheduling information.In the embodiment of FIG. 15(b), the first station STA1 receives abeacon frame from an access point AP. The first station STA1 obtainsinformation on UL MU transmission scheduling from the beacon frame. Whenthe information on the UL MU transmission scheduling obtained by thefirst station STA1 indicates that the UL MU transmission of the wirelesscommunication terminal is scheduled, the first station STA1 applies theMU EDCA parameter set. Thereafter, the first station STA1 receives thebeacon frame again from the access point AP. The first station STA1obtains information on UL MU transmission scheduling from the beaconframe. When the information on the UL MU transmission schedulingobtained by the first station STA1 indicates that the UL MU transmissionof the wireless communication terminal is not scheduled, the firststation STA1 switches from the MU EDCA parameter set to the general EDCAparameter set.

FIG. 16 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention applies an MUEDCA parameter.

As described above, when the wireless communication terminal applies theMU EDCA parameter, the wireless communication terminal may set the MUEDCA timer. In addition, as in the embodiment described with referenceto FIG. 14, the wireless communication terminal may set the MU EDCAtimer upon receiving the response to the trigger-based PPDUtransmission. Therefore, the wireless communication terminal may applythe MU EDCA parameter set upon receiving the response to thetrigger-based PPDU transmission. Specifically, when the wirelesscommunication terminal receives the response to the trigger-based PPDUtransmission, the wireless communication terminal may apply the MU EDCAparameter set. In a specific embodiment, the wireless communicationterminal may apply the MU EDCA parameter set when the following threeconditions are satisfied. The first condition is that the wirelesscommunication terminal receives the trigger frame that triggers thetransmission of the wireless communication terminal from the basewireless communication terminal. Specifically, the wirelesscommunication terminal receive the trigger frame indicating the AID ofthe wireless communication terminal. At this time, the trigger frame maybe a basic trigger frame. In a specific embodiment, the first conditionmay include the case where the User Info field of the trigger frameindicates random access and the wireless communication terminaltransmits the trigger-based PPDU through a random access. The secondcondition is to transmit the trigger-based PPDU including the QoS dataframe to the base wireless communication terminal according to thereception of the trigger frame. The third condition is that the wirelesscommunication terminal receives an immediate response to the triggerbased PPDU from the base wireless communication terminal. At this time,an immediate response may indicate that the recipient transmits aresponse to the originator within a predetermined time period during thesame transmit opportunity (TXOP). When these three conditions aresatisfied, the wireless communication terminal may apply the MU EDCAparameter set to the AC of the QoS data frame included in thetrigger-based PPDU transmitted by the wireless communication terminal.In addition, the wireless communication terminal may apply the MU EDCAparameter set at the time point at which the immediate responsereception for the trigger-based PPDU from the base wirelesscommunication terminal is completed. For example, the wirelesscommunication terminal may apply the MU EDCA parameter set at the timepoint at which the M-BA frame reception for the trigger-based PPDU fromthe base wireless communication terminal is completed. Also, when theconditions described above are satisfied before the MU EDCA timerexpires, the wireless communication terminal may update the MU EDCAtimer with a period corresponding to the MU EDCA parameter set. When theMU EDCA timer expires, the wireless communication terminal terminatesthe MU EDCA parameter set application.

In the embodiment of FIG. 16(a), the first station STA1 receives thetrigger frame TF from the base wireless communication terminal. At thistime, the trigger frame TF indicates the AID of the first station STA1.The first station STA1 transmits a trigger-based PPDU HE TRIG PPDUincluding an MPDU corresponding to TID1 and TID3 to the base wirelesscommunication terminal. The first station STA1 receives the M-BA framein response to the trigger-based PPDU HE TRIG PPDU from the basewireless communication terminal. When the first station STA1 completesreception of the M-BA frame, in relation to the first station STA1, thebase wireless communication terminal applies the MU EDCA parameter to anAC which the M-BA frame indicates as an ACK. At this time, the firststation STA1 sets the MU EDCA timer for an AC which the M-BA frameindicates as an ACK.

Even if a PPDU including an immediate response to a trigger-based PPDUfurther includes another frame, the wireless communication terminal mayapply the MU EDCA parameter set at the time point at which the immediateresponse reception for the trigger-based PPDU from the base wirelesscommunication terminal is completed. In an embodiment of FIG. 16(b), thebase wireless communication terminal transmits another frame DL togetherwhile transmitting the M-BA frame for the trigger-based PPDU HE TRIGPPDU to the first station STA1. When the first station STA1 completesthe reception of the PPDU including the M-BA frame and another frame DL,the first station STA1 applies the MU EDCA parameter to an AC which theM-BA frame indicates as an ACK. At this time, the first station STA1sets the MU EDCA timer for AC in which the M-BA frame indicates an ACK.

Also, when the downlink transmission and the uplink transmission arecontinuously performed in the same TXOP, the wireless communicationterminal may apply the MU EDCA parameter set to the end time point ofthe corresponding TXOP. In an embodiment of FIG. 16(c), the basewireless communication terminal transmits the M-BA frame for thetrigger-based PPDU HE TRIG PPDU transmitted by the first station STA1and another frame DL together as in the embodiment of FIG. 16(b). Atthis time, the first station STA1 performs uplink transmission to thebase wireless communication terminal again. When the first station SAT1receives a response to the uplink transmission, in relation to the firststation STA1, the base wireless communication terminal applies the MUEDCA parameter to an AC in which the M-BA frame indicates an ACK. Atthis time, the first station STA1 sets the MU EDCA timer for AC whichthe M-BA frame indicates as an ACK.

In another specific embodiment, under the condition that the wirelesscommunication terminal applies the MU EDCA parameter set, the triggerframe received by the wireless communication terminal may include atrigger frame variant such as a BSR poll frame. In addition, thewireless communication terminal may receive UL MU response schedulinginstead of the trigger frame. Specifically, when the wirelesscommunication terminal transmits the QoS data based on the trigger framevariant or the UL MU response scheduling, the wireless communicationterminal may apply the MU EDCA parameter set.

In the above-described embodiments, the wireless communication terminalmay determine the MU EDCA parameter set application time and the MU EDCAtimer setting time in consideration of the type of the respondingrequested by the MPDU included in the trigger-based PPDU. This will bedescribed with reference to FIGS. 17 to 18.

FIG. 17 shows an A-MPDU generated by a wireless communication terminalaccording to an embodiment of the present invention and a type ofresponding for a corresponding A-MPDU.

The wireless communication terminal may aggregate one or more MPDUs of aQoS data frame, an action frame, and a control frame into one PSDU andtransmit it to the A-MPDU. The A-MPDU including the QoS data frame maybe classified into the context of Data Enabled Immediate Response (DEIR)or Data Enabled No Immediate Response (DENIR) depending on whether QoSdata requests an Ack. The wireless communication terminal receiving theA-MPDU may determine whether the QoS data requests an Ack according tothe value of the ACK Policy subfield of the QoS Control field of the MACheader. At this time, the value of the ACK Policy subfield is indicatedfor each TID. In addition, the wireless communication terminal maydivide a service class of TID into QoSACK and QoSNoACK. The wirelesscommunication terminal transmitting the A-MPDU does not provide the BAagreement for the TID corresponding to the QoSNoACK service class. Inaddition, the wireless communication terminal transmitting the A-MPDUsets the value of the ACK Policy subfield of the TID corresponding tothe QoSNoACK service class to No ACK.

When the wireless communication terminal aggregates a plurality of MPDUscorresponding to one TID and transmits the A-MPDU, the immediateresponse context of the corresponding A-MPDU is determined according towhether the A-MPDU includes the MPDU of the TID requesting the ACK.Specifically, when the A-MPDU including only a plurality of MPDUscorresponding to one TID includes the MPDU of the TID requesting theACK, the immediate response context of the corresponding A-MPDU is DEIR.In addition, when the A-MPDU including only a plurality of MPDUscorresponding to one TID includes the MPDU of the TID not requesting theACK, the immediate response context of the corresponding A-MPDU isDENIR.

As described above, the wireless communication terminal may aggregate aplurality of MPDUs corresponding to a plurality of TIDs to generate amulti-TID A-MPDU. The immediate response context of the multi-TID A-MPDUmay be classified as follows. If the multi-TID A-MPDU includes one ormore TIDs requesting an ACK, the immediate response context of thecorresponding multi-TID A-MPDU is DEIR. Also, if the multi-TID A-MPDUincludes only a TID that does not request an ACK or a frame that doesnot have a TID, the immediate response context of the correspondingmulti-TID A-MPDU is DENIR. In the embodiment of FIG. 17(a), the A-MPDUincludes an MPDU with a TID of 1, an MPDU with a TIDR of 2, an MPDU witha TID of 3, and an action frame. An MPDU with a TID of 3 does notrequest an Ack, but each of an MPDU with a TID of 1, an MPDU with a TIDof 2, and an action frame requests an immediate response. Therefore, theimmediate response context of the A-MPDU is DEIR. In the embodiment ofFIG. 17(b), the A-MPDU includes an MPDU with a TID of 1, an MPDU with aTIDR of 2, an MPDU with a TID of 3, and an action No Ack frame. Each ofan MPDU with a TID of 1, an MPDU with a TID of 2, and an action framerequests an immediate response. All of an MPDU with a TID of 1, an MPDUwith a TID of 2, an MPDU with a TID of 3, and an action No ACK frame donot request an immediate response. Therefore, the immediate responsecontext of the A-MPDU is DENIR.

In the embodiments described with reference to FIG. 16, the wirelesscommunication terminal applies the MU EDCA parameter and sets the MUEDCA timer, based on the immediate response to the MPDU included in thetrigger-based PPDU. As described with reference to FIG. 17, the QoS dataframe included in the trigger-based PPDU may not request an Ack. Whenthe QoS data frame included in the trigger-based PPDU does not requestAck, the MU EDCA parameter set application operation and the MU EDCAtimer setting operation of the wireless communication terminal will bedescribed with reference to FIG. 18.

FIG. 18 shows an operation in which a wireless communication terminalaccording to another embodiment of the present invention applies an MUEDCA parameter.

When the QoS data frame included in the trigger-based PPDU transmittedby the wireless communication terminal does not request an ACK, thewireless communication terminal may apply the MU EDCA parameter set atthe time point at which transmission of the trigger-based PPDU ends. Inaddition, if the QoS data frame included in the trigger-based PPDUtransmitted by the wireless communication terminal does not request anACK, the wireless communication terminal may set the MU EDCA timer atthe time point at which transmission of the trigger-based PPDU ends. Asin the embodiment described with reference to FIG. 16, even if thewireless communication terminal receives a trigger frame variant ortransmits a trigger-based PPDU based on UL MU response scheduling, thewireless communication terminal may apply the MU EDCA parameter set atthe time point at which transmission of the trigger-based PPDU ends. Atthis time, the wireless communication terminal may set the MU EDCA timerat the time point at which transmission of the trigger-based PPDU ends.In another specific embodiment, when the immediate response context ofthe A-MPDU included in the trigger-based PPDU transmitted by thewireless communication terminal is DENIR, the wireless communicationterminal may apply the MU EDCA parameter set at the time point at whichtransmission of the trigger-based PPDU ends. In addition, when theimmediate response context of the A-MPDU included in the trigger-basedPPDU transmitted by the wireless communication terminal is DENIR, thewireless communication terminal may set the MU EDCA timer at the timepoint at which transmission of the trigger-based PPDU ends. In theembodiment of FIG. 18(a), the wireless communication terminal receivesthe trigger frame TF from the base wireless communication terminal. Uponreceiving the trigger frame, the wireless communication terminaltransmits a trigger-based PPDU HE TRIG PPDU including an A-MPDU whoseimmediate response context is DENIR to the base wireless communicationterminal. The wireless communication terminal applies the MU EDCAparameter set at the time point at which transmission of thetrigger-based PPDU HE TRIG PPDU ends and starts the MU EDCA timer.

In another specific embodiment, when the QoS data frame included in thetrigger-based PPDU transmitted by the wireless communication terminaldoes not request an ACK, the wireless communication terminal may applythe MU EDCA parameter set when a predetermined time elapses after thetime point at which transmission of the trigger-based PPDU ends. Inaddition, when the QoS data frame included in the trigger-based PPDUtransmitted by the wireless communication terminal does not request anACK, the wireless communication terminal may set the MU EDCA timer whena predetermined time elapses after the time point at which transmissionof the trigger-based PPDU ends. In another specific embodiment, when theimmediate response context of the A-MPDU included in the trigger-basedPPDU transmitted by the wireless communication terminal is DENIR, thewireless communication terminal may apply the MU EDCA parameter set whena predetermined time elapses after the time point at which transmissionof the trigger-based PPDU ends. In addition, if the immediate responsecontext of the A-MPDU included in the trigger-based PPDU transmitted bythe wireless communication terminal is DENIR, the wireless communicationterminal may set the MU EDCA timer when a predetermined time elapsesafter the time point at which transmission of the trigger-based PPDUends. At this point, the predetermined time may be a short inter framespace (SIFS). In another specific embodiment, the predetermined time maybe a time that is the sum of a predetermined representative ACKtransmission time and an SIFS. In the embodiment of FIG. 18(b), thewireless communication terminal receives the trigger frame TF from thebase wireless communication terminal. Upon receiving the trigger frame,the wireless communication terminal transmits a trigger-based PPDU HETRIG PPDU including an A-MPDU whose immediate response context is DENIRto the base wireless communication terminal. The wireless communicationterminal applies the MU EDCA parameter set when a predetermined timeelapses after the time point at which transmission of the trigger-basedPPDU HE TRIG PPDU ends and starts the MU EDCA timer. At this point, thepredetermined time may be an SIFS. In another specific embodiment, thepredetermined time may be a time that is the sum of the SIFS and thepredetermined representative ACK transmission time Ack time.

In another specific embodiment, if the QoS data frame included in thetrigger-based PPDU transmitted by the wireless communication terminaldoes not request an ACK, the wireless communication terminal may applythe MU EDCA parameter set based on an immediate response to thetrigger-based PPDU transmission of another wireless communicationterminal that transmits the trigger-based PPDU simultaneously with thewireless communication terminal. In another specific embodiment, whenthe immediate response context of the A-MPDU included in thetrigger-based PPDU transmitted by the wireless communication terminal isDENIR, the wireless communication terminal may apply the MU EDCAparameter set based on an immediate response to the trigger-based PPDUtransmission of another wireless communication terminal that transmitsthe trigger-based PPDU simultaneously with the wireless communicationterminal. In these embodiments, when the wireless communication terminalreceives an immediate response to the trigger-based PPDU transmission ofanother wireless communication terminal that transmits the trigger-basedPPDU simultaneously with the wireless communication terminal, thewireless communication terminal may apply the MU EDCA parameter set.When the wireless communication terminal does not receive an immediateresponse to the trigger-based PPDU transmission of another wirelesscommunication terminal that transmits the trigger-based PPDUsimultaneously with the wireless communication terminal, the wirelesscommunication terminal may apply the MU EDCA parameter set when apredetermined period elapses from when transmitting the trigger-basedPPDU transmitted by the wireless communication terminal. The time whenthe predetermined period elapses after transmitting the trigger-basedPPDU transmitted by the wireless communication terminal may be the timewhen it elapses by aSIFSTime+aSlotTime+aRxPHYStart-Delay from the timepoint after PHY-TXEND.confirm primitive.

In addition, if the QoS data frame included in the trigger-based PPDUtransmitted by the wireless communication terminal does not request anACK, the wireless communication terminal may set an MU EDCA timer basedon an immediate response to the trigger-based PPDU transmission ofanother wireless communication terminal that transmits the trigger-basedPPDU simultaneously with the wireless communication terminal. In anotherspecific embodiment, when the immediate response context of the A-MPDUincluded in the trigger-based PPDU transmitted by the wirelesscommunication terminal is DENIR, the wireless communication terminal mayset an MU EDCA timer based on an immediate response to the trigger-basedPPDU transmission of another wireless communication terminal thattransmits the trigger-based PPDU simultaneously with the wirelesscommunication terminal. In these embodiments, when the wirelesscommunication terminal receives an immediate response to thetrigger-based PPDU transmission of another wireless communicationterminal that transmits the trigger-based PPDU simultaneously with thewireless communication terminal, the wireless communication terminal mayset the MU EDCA timer. When the wireless communication terminal does notreceive an immediate response to the trigger-based PPDU transmission ofanother wireless communication terminal that transmits the trigger-basedPPDU simultaneously with the wireless communication terminal, thewireless communication terminal may set the MU EDCA timer when apredetermined period elapses from when transmitting the trigger-basedPPDU transmitted by the wireless communication terminal. The time whenthe predetermined period elapses after transmitting the trigger-basedPPDU transmitted by the wireless communication terminal may be the timewhen it elapses by aSIFSTime+aSlotTime+aRxPHYStart-Delay from the timepoint after PHY-TXEND.confirm primitive.

In the embodiment of FIG. 18(c), the wireless communication terminalreceives a trigger frame TF and transmits a trigger-based PPDU HE TRIGPPDU including an A-MPDU whose immediate response context is DENIR tothe base wireless communication terminal. When the wirelesscommunication terminal transmits a trigger-based PPDU HE TRIG PPDU, thewireless communication terminal simultaneously detects the M-BA frametransmission for the trigger-based PPDU of another wirelesscommunication terminal that transmits the trigger-based PPDU. Thewireless communication terminal applies the MU EDCA parameter set at thetime point at which reception of the M-BA frame for the trigger-basedPPDU of another wireless communication terminal ends, and starts the MUEDCA timer. When the wireless communication terminal does not receivethe M-BA frame for the trigger-based PPDU of another wirelesscommunication terminal as in the embodiment of FIG. 18(d), the wirelesscommunication terminal applies the MU EDCA parameter set at the timepoint at which it elapses by aSIFSTime+aSlotTime+aRxPHYStart-Delay fromwhen transmitting the trigger-based PPDU HE TRIG PPDU, and starts the MUEDCA timer.

In these embodiments, the wireless communication terminal may apply theMU EDCA parameter set to the AC corresponding to the QoS data frametransmitted through the trigger-based PPDU as in the embodimentdescribed with reference to FIG. 16.

In another specific embodiment, when a wireless communication terminaltransmits a trigger-based PPDU, the wireless communication terminal maybe restricted not to transmit a QoS data frame that does not request anACK. Specifically, when the wireless communication terminal transmitsthe trigger-based PPDU, the wireless communication terminal may berestricted not to transmit the QoS data frame with the Ack policysubfield set to No Ack.

The operation of the wireless communication terminal to apply a separateMU EDCA parameter set will be described with reference to FIGS. 19 to21.

FIG. 19 shows an operation in which a wireless communication terminalaccording to an embodiment of the present invention applies an MU EDCAparameter set.

As described above, the EDCA parameter set may include a backoff timerand a parameter related to CW. When the wireless communication terminalswitches the currently used first EDCA parameter set to the second EDCAparameter set, the wireless communication terminal may change the valueof the backoff timer currently used in the backoff procedure based onthe second EDCA parameter set. At this time, the first EDCA parameterset may be a general EDCA parameter set, and the second EDCA parameterset may be an MU EDCA parameter set. Also, the first EDCA parameter setmay be an MU EDCA parameter set and the second EDCA parameter set may bea general EDCA parameter set. This is because if the wirelesscommunication terminal does not change the value of the backoff timerwhen switching the EDCA parameter set, the effect of changing thechannel access priority caused by the switching of the EDCA parameterset may not be immediately applied.

In a specific embodiment, the wireless communication terminal maymultiply the backoff timer currently used in the backoff procedure witha value determined based on the second EDCA parameter set. At this time,the value determined based on the second EDCA parameter set may be avalue determined based on the CW parameter value of the second EDCAparameter set. Specifically, a value determined based on the secondparameter set may be a value obtained by dividing the CWmin of thesecond EDCA parameter set by the CWmin of the first EDCA parameter set.In another specific embodiment, the value determined based on the secondEDCA parameter set may be a value obtained by dividing the CWmax of thesecond EDCA parameter set by the CWmax of the first EDCA parameter set.In another specific embodiment, when the value of the backoff timercurrently used by the wireless communication terminal in the backoffprocedure is smaller than the CWmin of the second EDCA parameter set,the wireless communication terminal may set the value of the backofftimer to the CWmin of the second EDCA parameter set. In addition, whenthe value of the backoff timer currently used by the wirelesscommunication terminal in the backoff procedure is greater than theCWmax of the second EDCA parameter set, the wireless communicationterminal may set the value of the backoff timer to the CWmax of thesecond EDCA parameter set.

When the wireless communication terminal switches the currently usedfirst EDCA parameter set to the second EDCA parameter set, the wirelesscommunication terminal may change the parameter value for CW currentlyused in the backoff procedure based on the second EDCA parameter set. Atthis time, the parameter for CW may include CWmin and CWmax. Also, theEDCA parameter set may include a short retry limit and a long retrylimit, which are parameters for adjusting the CW value according to thenumber of channel retransmission attempts. Also, the first EDCAparameter set may be a general EDCA parameter set and the second EDCAparameter set may be an MU EDCA parameter set. Also, the first EDCAparameter set may be an MU EDCA parameter set and the second EDCAparameter set may be a general EDCA parameter set. The wirelesscommunication terminal may increase the value of CW in the backoffprocedure. At this time, the value of CW is limited to the value ofCWmax, and the wireless communication terminal may reset the value of CWto CWmin according to the retry limit value. This is because therestriction may not be applied when the wireless communication terminalswitches the EDCA parameter set.

Specifically, when the CW value currently used by the wirelesscommunication terminal in the backoff procedure is smaller than theCWmin of the second EDCA parameter set, the wireless communicationterminal may set the CW value to CWmin of the second EDCA parameter set.In addition, when the CW value currently used by the wirelesscommunication terminal in the backoff procedure is greater than theCWmax of the second EDCA parameter set, the wireless communicationterminal may set the CW value to the CWmax of the second EDCA parameterset. In addition, if the QoS short retry counter (QSRC) is greater thanthe short retry limit or the QoS long retry counter (QLRC) is greaterthan the short retry limit, the wireless communication terminal may setthe CW value to the CWmin of the second EDCA parameter set.

In the embodiment of FIG. 19, the wireless communication terminalswitches the legacy EDCA parameter set for the AC BE to the MU EDCAparameter set. At this time, the wireless communication terminal setsthe backoff timer value BO_(MU)[BE] to the product of a value a[AC]obtained based on the MU EDCA parameter set and the value of the backofftimer BO[BE] in the current backoff procedure. Also, the wirelesscommunication terminal sets the CW value CWmu[BE] to a larger value ofthe CW value CW[BE] in the current backoff procedure and CWmin CWmin[BE]in the MU EDCA parameter set. When the wireless communication terminalconverts the MU EDCA parameter set into a general EDCA parameter set,the wireless communication terminal sets the CW value CW[BE] to asmaller value of CW CWmu[BE] value in the current backoff procedure andCWmax CWmax[BE] of the Legacy EDCA parameter set.

The specific operation of the wireless communication terminal to set theCW will be further described with reference to FIG. 20 and followingdrawings.

FIG. 20 shows an operation of changing a CW value while a wirelesscommunication terminal according to an embodiment of the presentinvention changes an EDCA parameter set.

The wireless communication terminal changes the CW value in thefollowing three situations during the backoff procedure.

1) When the transmission of the initial PPDU of the TXOP fails and theAC of the MPDU is the primary AC

2) When two or more EDCAFs contend in the same wireless communicationterminal and the transmission attempt of the wireless communicationterminal collides with another EDCAF having a higher priority in thewireless communication terminal

3) PHY-TXBUSY.indication (BUSY) primitive is responded with respect toPHYTXSTART.request primitive and when a transmission attempt of awireless communication terminal coordinated by a multiple MAC-stationmanagement entity (MM-SME) collides with a transmission attempt ofanother wireless communication terminal coordinated by the same MM-SME

At this time, the wireless communication terminal changes the CW valueaccording to the following rule.

a) When QSRC QSRC[AC] corresponding to the AC reaches the short retrylimit dot11ShortRetryLimit) or QLRC QLRC[AC] corresponding to the ACreaches the long retry limit dot11LongRetryLimit, the wirelesscommunication terminal resets the CW value CW[AC] corresponding to theAC to the CWmin value CWmin [AC].

b) When the value of dot11RobustAVStreamingImplemented is true, and theQoS short drop retry count QSDRC[AC] corresponding to the AC reachesdot11ShortDEIRetryLimit, or the QoS long drop retry count QLDRC[AC] forAC reaches dot11LongDEIRetryLimit, the wireless communication terminalresets the CW value CW[AC] corresponding to the AC to the CWmin valueCWmin[AC].

c) Otherwise

c-1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto (CW[AC]+1)×2−1.

c-2) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

The situations of 1), 2) and 3) are all cases where the wirelesscommunication terminal retries transmission due to transmission failure,internal contention failure, and the like. Also, in a) and b), thewireless communication terminal resets the CW value due to exceeding thenumber of retries. In c), the wireless communication terminal changesthe CW value to retry the transmission. In a), b), and c), the wirelesscommunication terminal operates without considering the case where theEDCA parameter set is changed. For example, the CW value correspondingto the AC is equal to CWmin, and the wireless communication terminal mayapply the EDCA parameter set having the CWmin larger than the previousEDCA parameter set. At this time, the wireless communication terminaluses a CW value smaller than the CWmin of the new EDCA parameter set.Also, the CW value corresponding to the AC is equal to CWmax, and thewireless communication terminal may apply the EDCA parameter set havingCWmax smaller than the previous EDCA parameter set. At this time, thewireless communication terminal uses a CW value greater than the CWmaxof the new EDCA parameter set. At this time, since this does notcorrespond to the conditions c-1) and c-2) described above, the wirelesscommunication terminal may not change the CW value within the range ofCWmin and CWmax. Therefore, the operation of the wireless communicationterminal in c) may be changed as follows.

c-1) In case of a legacy wireless communication terminal (e.g., non-HESTA)

c-1-1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto (CW[AC]+1)×2−1.

c-2-2) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-2) In case of a non-legacy wireless communication terminal (e.g., HESTA)

c-2−1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmin value CWmin[AC], the wireless communication terminal sets theCW value CW[AC] corresponding to the AC to the CWmin value CWmin[AC].

c-2-2) When the CW value CW [AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto (CW[AC]+1)×2−1.

c-2-3) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-2-4) When the CW value CW[AC] corresponding to the AC is greater thanthe CWmax value CWmax[AC], the wireless communication terminal sets theCW value CW[AC] corresponding to the AC to the CWmax value CWmax[AC].

In another embodiment, the wireless communication terminal may operateas follows in the above-mentioned c).

c-1) In case of a legacy wireless communication terminal (e.g., non-HESTA)

c-1-1) When the CW value CW [AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto (CW[AC]+1)×2−1.

c-2-2) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-2) In case of a non-legacy wireless communication terminal (e.g., HESTA)

c-2−1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto a larger value of (CW[AC]+1)×2−1 and the CWmin value CWmin[AC].

c-2-2) When the CW value CW[AC] corresponding to the AC is equal to orgreater than the CWmax value CWmax[AC] corresponding to the AC, thewireless communication terminal sets the CW value CW[AC] correspondingto the AC to the CWmax value CWmax[AC].

In another embodiment, the wireless communication terminal may operateas follows in the above-mentioned c).

c-1) In case of a legacy wireless communication terminal (e.g., non-HESTA)

c-1-1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto (CW[AC]+1)×2−1.

c-2-2) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-2) In case of a non-legacy wireless communication terminal (HE STA)

c-2−1) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto a larger value of CW[AC]+1)×2−1 and the CWmin value CWmin[AC].

c-2-2) If the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-2-3) If the CW value CW[AC] corresponding to the AC is greater thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto the CWmax value CWmax [AC].

FIG. 21 shows an operation of changing a CW value while a wirelesscommunication terminal according to an embodiment of the presentinvention changes an EDCA parameter set.

In the embodiment described with reference to FIG. 20, only theoperation of the non-legacy wireless communication terminal HE STA isconsidered. However, a similar problem may occur in a legacy wirelesscommunication terminal non-HE STA to which an MU EDCA parameter set isapplied. This is because the legacy wireless communication terminal(e.g., non-HE STA) may change some of the values of the EDCA parameterset. Therefore, the wireless communication terminal may operate asfollows in the above-mentioned c).

c) Otherwise

c-1-3) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmin value CWmin[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto the CWmin value CWmin [AC].

c-2) When the CW value CW[AC] corresponding to the AC is larger than theCWmin value CWmin[AC] corresponding to AC and equal to or smaller thanthe CWmax value CWmax[AC], the wireless communication terminal sets theCW value CW[AC] corresponding to AC to (CW[AC]+1)×2−1.

c-3) When the CW value CW[AC] corresponding to the AC is greater thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto the CWmax value CWmax [AC].

In another embodiment, the wireless communication terminal may operateas follows in the above-mentioned c).

c) Otherwise

c-1-3) When the CW value CW[AC] corresponding to the AC is smaller thanthe CWmin value CWmin[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto the CWmin value CWmin [AC].

c-2) When the CW value CW[AC] corresponding to the AC is larger than theCWmin value CWmin[AC] corresponding to AC and smaller than the CWmaxvalue CWmax[AC], the wireless communication terminal sets the CW valueCW[AC] corresponding to AC to (CW[AC]+1)×2−1.

c-3) When the CW value CW[AC] corresponding to the AC is equal to theCWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal does not change the CW value CW[AC] correspondingto the AC.

c-4) When the CW value CW[AC] corresponding to the AC is greater thanthe CWmax value CWmax[AC] corresponding to the AC, the wirelesscommunication terminal sets the CW value CW[AC] corresponding to the ACto the CWmax value CWmax [AC].

In another embodiment, the wireless communication terminal may operateas follows in the above-mentioned c).

c) Otherwise

c-1) When the CW value (CW [AC]) corresponding to the AC is smaller thanthe CWmax value (CWmax[AC]), the wireless communication terminal setsthe CW value (CW[AC]) corresponding to the AC to (CW[AC]+1)×2−1.

c-2) When the CW value (CW[AC]) corresponding to the AC is equal to orgreater than the CWmax value (CWmax[AC]) corresponding to the AC, thewireless communication terminal sets the CW value (CW[AC]) correspondingto the AC to the CWmax value (CWmax [AC]).

As described above, the base wireless communication terminal may signalinformation on the MU EDCA parameter set. The specific format of theinformation on the MU EDCA parameter set will be described withreference to FIG. 22 to FIG. 23.

FIG. 22 shows a specific format of an MU EDCA parameter set elementaccording to an embodiment of the present invention.

The MU EDCA parameter set element according to an embodiment of thepresent invention includes an Element ID field and an Element IDextension field for identifying the MU EDCA parameter set element. Inaddition, the MU EDCA parameter set element includes an MU EDCA QoS Infofield. The MU EDCA QoS Info field may include an MU EDCA Parameter SetUpdate Count field whose value is changed whenever the MU EDCA parameterset is changed. Specifically, when the base wireless communicationterminal changes the MU EDCA parameter set, the base wirelesscommunication terminal may increment the value of the MU EDCA ParameterSet Update Count field by one. The wireless communication terminalreceiving the MU EDCA parameter set element may determine whether tochange the MU EDCA parameter set based on the MU EDCA Parameter SetUpdate Count field value. Other fields in the MU QoS Info field otherthan the MU EDCA Parameter Set Update Count field may have the sameformat as the EDCA QoS Info field.

In addition, the MU EDCA parameter set element may include informationon the MU EDCA timer. Specifically, the MU EDCA parameter set elementmay include information indicating the expiration time of the MU EDCAtimer.

In addition, the MU EDCA parameter set element includes a plurality ofMU AC Parameter Record fields indicating information corresponding toeach AC. Specifically, the MU EDCA parameter set element includes an MUAC_BE Parameter Record field, an MU AC_BK Parameter Record field, an MUAC_VI Parameter Record field, and an MU AC_VO Parameter Record field.The MU AC Parameter Record field may include an ACI/AIFSN field and anECWmin/ECWmax field. The wireless communication terminal receiving theMU EDCA parameter set element applies the MU EDCA parameter setinformation corresponding to each AC based on the MU AC Parameter Recordfield. Specifically, the wireless communication terminal receiving theMU EDCA parameter set element sets a management information base (MIB)attribute based on the MU AC Parameter Record field.

FIG. 23 shows a specific format of an MU EDCA parameter set elementaccording to another embodiment of the present invention.

Even if the base wireless communication terminal does not transmit theMU EDCA parameter set element in the beacon frame, the base wirelesscommunication terminal may transmit the MU QoS Info field using thebeacon frame. Specifically, the base wireless communication terminal maytransmit the MU QoS Info field through an element other than the MU EDCAparameter set element. In a specific embodiment, the base wirelesscommunication terminal may transmit the MU QoS Info field through aQoS-related element other than the MU EDCA parameter set element.

In another specific embodiment, the base wireless communication terminalmay transmit an MU EDCA parameter set element that does not include anMU QoS Info field. At this time, the specific format of the MU EDCAparameter set element may be as shown in FIG. 23. The wirelesscommunication terminal receiving the QoS Info field may determinewhether the wireless communication terminal may not apply the changedEDCA parameter set based on the EDCA Parameter Set Update Count field.When it is determined that the wireless communication terminal does notapply the changed EDCA parameter set and the beacon frame does notinclude the EDCA parameter set element, the wireless communicationterminal may request the transmission of the EDCA parameter set elementby transmitting the probe request frame to the base wirelesscommunication terminal. When the base wireless communication terminal isnot allowed to transmit the MU QoS Info field together with otherelements other than the MU EDCA parameter set element, the MU QoS Infofield may not perform the same role as the QoS Info field describedabove and the need to transmit the MU QoS Info field is also eliminated.Thus, when it is not allowed to transmit the MU QoS Info field togetherwith other elements other than the MU EDCA parameter set element, thebase wireless communication terminal may transmit an MU EDCA parameterset element that does not include the MU QoS Info field.

The wireless communication terminal performs an internal contentionprocedure for data corresponding to each of a plurality of ACs using aninternal EDCA queue. Specifically, the wireless communication terminalmay operate a plurality of EDCA queues classified according to theaccess category of data stored in the queue. In addition, the wirelesscommunication terminal may perform a backoff procedure for accessing achannel based on a time corresponding to a backoff timer in each of aplurality of EDCA queues. At this time, a method of using the EDCA queueby the wireless communication terminal will be described in detail withreference to FIG. 24 to FIG. 27.

FIG. 24 shows an EDCA operation after UL MU transmission of a wirelesscommunication terminal according to an embodiment of the presentinvention.

The wireless communication terminal may operate as follows at theboundary of each slot in the backoff procedure.

1) When the backoff timer is not 0, the wireless communication terminaldecrements the value of the backoff timer by one.

2) When data is present in the EDCA queue, and the backoff timer is 0,and transmission is not attempted in another EDCA queue with a high userpriority (UP), the wireless communication terminal starts a transmissionsequence for the data of the corresponding EDCA queue.

3) When data is present in the EDCA queue, and the backoff timer is 0,and transmission is attempted in another EDCA queue with a high userpriority (UP), the wireless communication terminal performs an operationaccording to an internal collision.

4) When other situations, the wireless communication terminal does notperform any operation.

However, when the back off timer is 0 and the EDCA queue of the wirelesscommunication terminal is empty, there is a problem because it is notclearly defined that what kind of operation the wireless communicationterminal should perform. Specifically, in the following situations, whenthe backoff timer is 0, the EDCA queue of the wireless communicationterminal may be empty.

As described above, the base wireless communication terminal may triggerthe uplink transmission of the wireless communication terminal bytransmitting the trigger information. At this time, the base wirelesscommunication terminal may obtain TXOP for transmission of triggerinformation through a backoff procedure. Therefore, the wirelesscommunication terminal may maintain the backoff timer for AC of the datatransmitted through the UL MU transmission in a state before the UL MUtransmission. At this time, the wireless communication terminal mayattempt to access the channel by resuming the backoff procedure for thecorresponding AC. Data may not reach the EDCA queue of the AC until thebackoff timer reaches 0.

Also, as described with reference to FIGS. 19 to 21, if it is not thecase where the wireless communication terminal attempts transmission andfails, even when the EDCA parameter set is changed, the CW value may bemaintained as it is. Also, when the EDCA queue of the corresponding ACis empty and new data arrives in the corresponding EDCA queue, thewireless communication terminal obtains a random integer value withinthe current CW and sets a backoff timer. Thus, the wirelesscommunication terminal may obtain a new backoff timer using the CWcalculated according to the previous EDCA parameter set. For example, inthe embodiment of FIG. 24, the wireless communication terminal receivesthe trigger frame TF from the base wireless communication terminal. Atthis time, the wireless communication terminal stops the back offprocedure for data in which AC is VO. The wireless communicationterminal maintains the backoff timer of 4 and the CW value of 127. Thewireless communication terminal transmits a trigger-based PPDU includingQoS data TID 1 and TID 3 in which AC is VO to the base wirelesscommunication terminal based on the trigger frame. The wirelesscommunication terminal receives the M-BA frame from the base wirelesscommunication terminal. The wireless communication terminal receives theM-BA frame and applies the MU EDCA parameter set as described above.Thereafter, the wireless communication terminal restarts the backoffprocedure in which the value of the backoff timer is 4 and the CW valueis 127. The channel accessed by the wireless communication terminal isidle for the time corresponding to the AIFS and the time correspondingto the backoff timer value of 4. Therefore, the back off timer becomes0. However, since the wireless communication terminal transmits all datain which AC is VO using the trigger-based PPDU, the EDCA queue for theVO is empty. When new data arrives in the EDCA queue for the VO of thewireless communication terminal, the wireless communication terminalobtains the random value of 66 within the existing CW value of 127 andsets it as the back off timer value regardless of CWmin and CWmax of theMU EDCA parameter set. Also, regardless of UL MU transmission, if theEDCA queue is empty and the backoff timer is 0, this may happen in thefollowing situations. The wireless communication terminal transmits alldata of the EDCA queue for the primary AC, and until the value of thebackoff timer reaches 0, additional data may not arrive in the EDCAqueue for the primary AC. Also, when the base wireless communicationterminal performs DL MU transmission using MU-MIMO or DL OFDMA, the basewireless communication terminal may occupy the channel with the primaryAC and transmit the data corresponding to the AC other than the primaryAC together with the data corresponding to the primary AC. At this time,a backoff timer corresponding to AC other than the primary AC remains,and the EDCA queue of the corresponding AC may be empty. In addition, if(A-)MSDU corresponding to any AC among the AC with the BA agreementremains and the lifetime of the corresponding MSDU expires, the wirelesscommunication terminal may discard the corresponding (A-) MSDU. At thistime, when the EDCA queue for any AC of the wireless communicationterminal is empty, the back off timer may reach 0. If the EDCA queue isempty and the backoff timer is 0, the operation of the wirelesscommunication terminal at the slot boundary will be described in detailwith reference to FIGS. 25 to 27.

FIG. 25 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according to anembodiment of the present invention is empty and the backoff timer is 0.

When the EDCA queue is empty and the backoff timer is 0, the wirelesscommunication terminal may not perform any operation at the slotboundary. Specifically, the wireless communication terminal may maintainthe backoff timer to be 0. Also, the wireless communication terminal maynot start the transmission sequence. In a specific embodiment, thewireless communication terminal may maintain all state variables of theEDCA function (EDCAF) without modification. In the embodiment of FIG.25, when the EDCA queue of the wireless communication terminal for VO isempty, the backoff timer BO[VO] reaches 0. At this time, the wirelesscommunication terminal does not perform any operation.

FIG. 26 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according toanother embodiment of the present invention is empty and the backofftimer is 0.

When the EDCA queue is empty and the backoff timer is 0, the wirelesscommunication terminal may resume the backoff procedure at the slotboundary. At this time, the wireless communication terminal may maintainthe CW value without modification. This is because it is not the casethat the wireless communication terminal fails to transmit, and there isno need to double CW. Specifically, the wireless communication terminalmay maintain all the state variables of the EDCAF except for the backofftimer. Also, when the EDCA queue is empty and the backoff timer is 0again, the wireless communication terminal may start the backoffprocedure again. In the embodiment of FIG. 26, when the EDCA queue ofthe wireless communication terminal for VO is empty, the backoff timerBO[VO] reaches 0. The wireless communication terminal obtains a randomvalue of 10 within the CW CW[VO] corresponding to the VO whilemaintaining all other EDCAF state variables, and sets the backoff timerBO[VO] using 10.

FIG. 27 shows the operation of a wireless communication terminal whenthe EDCA queue of the wireless communication terminal according toanother embodiment of the present invention is empty and the backofftimer is 0.

When the EDCA queue is empty and the backoff timer is 0, the wirelesscommunication terminal may initiate the EDCAF at the slot boundary. Atthis time, the wireless communication terminal may set CW to CWmin.Also, the wireless communication terminal may set QSRC and OLRC toinitial values. Specifically, the wireless communication terminal mayset QSRC and OLRC to 0. The wireless communication terminal initializesthe EDCAF and then starts the backoff procedure again. At this time, thewireless communication terminal may maintain the CW value withoutmodification. This is because it is not the case that the wirelesscommunication terminal fails to transmit, and there is no need to doubleCW.

In addition, when the EDCA queue is empty and the backoff timer is 0again, the wireless communication terminal may initiate the EDCAF at theslot boundary again. When the state variable of the EDCAF maintains theinitial value to prevent meaningless initialization, the wirelesscommunication terminal may not perform initialization.

FIG. 28 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

The wireless communication terminal according to an embodiment of thepresent invention accesses the channel according to the priority of datato be transmitted (S2801). Specifically, the wireless communicationterminal may access the channel according to the EDCA proceduredescribed above. At this time, the wireless communication terminal maybe a base wireless communication terminal. In addition, the wirelesscommunication terminal may be a wireless communication terminalassociated with the base wireless communication terminal.

The wireless communication terminal that wirelessly communicates with abase wireless communication terminal may switch a parameter set used forchannel access from a first parameter set to a second parameter setbased on whether the UL MU transmission is scheduled. Specifically, thewireless communication terminal may switch the parameter set used forchannel access from the first parameter set to the second parameter setbased on whether the base wireless communication terminal triggers theUL MU transmission participation of the wireless communication terminal.Further, the base wireless communication terminal transmits a triggerframe to the wireless communication terminal, and the base wirelesscommunication terminal may trigger the UL MU transmission participationof the wireless communication terminal. Depending on whether the userinfo field of the trigger frame includes the AID of the wirelesscommunication terminal, the wireless communication terminal maydetermine whether the base wireless communication terminal triggers theUL MU transmission participation of the wireless communication terminal.

At this time, the parameter set used for the channel access may be a setof parameters used to access the channel according to the priority ofthe data. Specifically, the parameter set used for channel access may bethe EDCA parameter set described above. Specifically, the EDCA parameterset may include parameters for CW. At this time, the parameter for CWmay include at least one of CWmin and CWmax. In addition, the EDCAparameter set may include a parameter value related to a predeterminedtime at which the wireless communication terminal waits to start thebackoff procedure. At this time, the predetermined time may be the AIFSdescribed above.

In addition, the wireless communication terminal may determine whetherto switch from the first parameter set to the second parameter set foreach access category of data. Further, when the wireless communicationterminal transmits the BSR, the wireless communication terminal mayswitch from the first parameter set to the second parameter set. Inanother specific embodiment, the wireless communication terminal mayswitch from the first parameter set to the second parameter set when thewireless communication terminal obtains information on the UL MUtransmission. In another specific embodiment, the wireless communicationterminal may transmit the trigger-based PPDU to the base wirelesscommunication terminal according to the triggering of the base wirelesscommunication terminal. At this time, the wireless communicationterminal may switch from the first parameter set to the second parameterset according to an immediate response to the MPDU included in thetrigger-based PPDU. At this time, the wireless communication terminalmay switch from the first parameter set to the second parameter set whenthe wireless communication terminal receive an immediate response to theMPDU included in the trigger-based PPDU. The MPDU included in thetrigger-based PPDU may be a QoS data frame.

When the second parameter set application condition is not satisfieduntil a certain time elapses from when the timer is set, the wirelesscommunication terminal may set the second parameter set timer forterminating the MU EDCA parameter set application. Specifically, basedon whether the wireless communication terminal receives an immediateresponse to the MPDU included in the trigger-based PPDU, the wirelesscommunication terminal may set the second parameter set timer accordingto the immediate response reception. When the second parameter set timerexpires, the wireless communication terminal may be allowed to terminatethe second parameter set application. Further, when the wirelesscommunication terminal switches from the first parameter set to thesecond parameter set, the wireless communication terminal may set thesecond parameter set timer. In addition, the wireless communicationterminal may determine when to switch from the first parameter set tothe second parameter set based on the type of responding requested bythe MPDU included in the trigger-based PPDU. In addition, the wirelesscommunication terminal may determine when to set the second parameterset timer based on the type of responding requested by the MPDU includedin the trigger-based PPDU. When the MPDU included in the trigger-basedPPDU transmitted by the wireless communication terminal does not requestthe ACK, the wireless communication terminal may set the secondparameter set timer when the transmission of the trigger-based PPDUends. In addition, the wireless communication terminal may set a secondparameter set timer for each access category. Specifically, when theMPDU included in the trigger-based PPDU does not request an ACK, thewireless communication terminal may switch the parameter set from thefirst parameter set to the second parameter set and set the secondparameter set timer when the transmission of the trigger based PPDUends. As described above, the MPDU included in the trigger-based PPDUmay be a QoS data frame. The specific operation of the wirelesscommunication terminal may be the same as that described with referenceto FIG. 6 through FIG. 18.

In addition, while the wireless communication terminal performs thebackoff procedure, the parameters of the parameter set used in thebackoff procedure may be changed. When the CW value is larger thanCWmax, the wireless communication terminal may set the CW value toCWmax. In addition, when the CW value is smaller than CWmin, thewireless communication terminal may set the CW value to CWmin.Specifically, when the wireless communication terminal switches thecurrently used first parameter set to the second parameter set, thewireless communication terminal may change the value of the backofftimer currently used in the backoff procedure based on the secondparameter set. In a specific embodiment, the wireless communicationterminal may multiply the backoff timer currently used in the backoffprocedure with a value determined based on the second parameter set.When the wireless communication terminal switches the currently usedfirst parameter set to the second parameter set, the wirelesscommunication terminal may change the parameter value for CW currentlyused in the backoff procedure based on the second parameter set. At thistime, the parameter for CW may include CWmin and CWmax. Specifically,the wireless communication terminal may operate in the same manner asthe embodiments described with reference to FIGS. 19 to 21.

The wireless communication terminal may operate a plurality of queuesclassified according to the access category of data stored in the queue.In addition, the wireless communication terminal may perform a backoffprocedure for accessing a channel based on a time corresponding to abackoff timer in each of a plurality of queues. At this time, the queuemay represent the EDCA queue described above. When there is no datastored in the queue and the backoff timer corresponding to the queue is0, the wireless communication terminal may not perform any operation atthe slot boundary. At this time, the wireless communication terminal maymaintain the backoff timer to be 0. In another specific embodiment, thewireless communication terminal may resume the backoff procedure at theslot boundary. At this time, the wireless communication terminal maymaintain the CW value without modification. In another specificembodiment, the wireless communication terminal may initialize a set ofchannel access parameters at a slot boundary. At this time, the wirelesscommunication terminal may set CW to CWmin. Also, the wirelesscommunication terminal may set QSRC and OLRC to initial values.Specifically, the wireless communication terminal may set QSRC and OLRCto 0. Specifically, the wireless communication terminal may operate inthe same manner as the embodiments described with reference to FIGS. 24to 27.

The wireless communication terminal transmits the data through theaccessed channel (S2803).

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

1. A wireless communication terminal that wirelessly communicates with abase wireless communication terminal, the wireless communicationterminal comprising: a transceiver; and a processor for processing aradio signal received through the transceiver or a radio signal to betransmitted through the transceiver, wherein the processor is configuredto access a channel according to a priority of data to be transmitted tothe base communication terminal by the wireless communication terminal.2. The wireless communication terminal of claim 1, wherein the processoris configured to switch a parameter set, which is a set of parametersused for the channel access, from a first parameter set to a secondparameter set based on whether the base wireless communication terminaltriggers a multi-user uplink transmission participation of the wirelesscommunication terminal.
 3. The wireless communication terminal of claim2, wherein the processor is configured to transmit the trigger-basedphysical layer protocol data unit (PPDU) to the base wirelesscommunication terminal using the transceiver, set a second parameter settimer according to an immediate response reception based on whether animmediate response to a MAC protocol data unit (MPDU) included in thetrigger-based PPDU is received, and when the second parameter set timerexpires, terminate the application of the second parameter set.
 4. Thewireless communication terminal of claim 3, wherein the processor isconfigured to set the second parameter set timer when the immediateresponse reception ends.
 5. The wireless communication terminal of claim3, wherein the processor is configured to set the second parameter settimer for an access category of an MPDU for which the immediate responseis received.
 6. The wireless communication terminal of claim 3, whereinthe processor is configured to determine when to set the secondparameter set timer based on a type of responding requested by the MPDUincluded in the trigger-based PPDU.
 7. The wireless communicationterminal of claim 6, wherein when the MPDU included in the trigger-basedPPDU does not request an ACK, the processor is configured to set thesecond parameter set timer when the transmission of the trigger-basedPPDU ends.
 8. The wireless communication terminal of claim 3, whereinthe MPDU included in the trigger-based PPDU is a QoS data frame.
 9. Thewireless communication terminal of claim 3, wherein the processor isconfigured to receive a beacon frame from the base wirelesscommunication terminal and obtain information indicating a period of thesecond parameter set timer from the beacon frame.
 10. The wirelesscommunication terminal of claim 3, wherein when switching the parameterset from the first parameter set to the second parameter set, theprocessor is configured to set the second parameter set timer.
 11. Thewireless communication terminal of claim 2, wherein the processor isconfigured to calculate a random integer value within a contentionwindow (CW), set a backoff timer based on the random integer value, andaccess a channel based on the back off timer and a predetermined slottime, wherein the parameter set comprises a minimum value (CWmin) of theCW and a maximum value (CWmax) of the CW.
 12. The wireless communicationterminal of claim 1, wherein the processor is configured to calculate arandom integer value in a contention window (CW), set a backoff timerbased on the random integer value, access a channel based on the backoff timer and a predetermined slot time, and if a value of the CW isgreater than the maximum value (CWmax) of the CW according to a priorityof the traffic, sets the value of the CW to the CWmax.
 13. The wirelesscommunication terminal of claim 1, wherein the processor is configuredto operate a plurality of queues that are classified according to anaccess category of data stored in a queue and performs backoff procedureof accessing a channel based on a time corresponding to a backoff timerin each of the plurality of queues, and when there is no data stored inthe queue and the backoff timer corresponding to the queue is 0, performno operation at a slot boundary of the backoff timer, wherein thebackoff timer is set based on a random integer value calculated in acontention window (CW), and is reduced when the channel is idle for apredetermined slot time.
 14. The wireless communication terminal ofclaim 13, wherein when there is no data stored in the queue and thebackoff timer corresponding to the queue is 0, the processor isconfigured to maintain the backoff timer to be
 0. 15. An operationmethod of a wireless communication terminal that wirelessly communicateswith a base wireless communication terminal, the method comprising:accessing a channel according to a priority of data to be transmitted tothe base wireless communication terminal; and transmitting the datathrough the channel.
 16. The method of claim 15, wherein the accessingof the channel comprises: switching a parameter set, which is a set ofparameters used for the channel access, from a first parameter set to asecond parameter set based on whether the base wireless communicationterminal triggers a multi-user uplink transmission participation of thewireless communication terminal; and accessing a channel using a secondset of parameters based on a priority of the traffic to be transmittedto the base communication terminal by the wireless communicationterminal.
 17. The method of claim 16, further comprising transmitting atrigger-based PPDU to the base wireless communication terminal using thetransceiver, wherein the switching from the first parameter set to thesecond parameter set comprises: setting a second parameter set timeraccording to an immediate response reception based on whether animmediate response to a MAC protocol data unit (MPDU) included in thetrigger-based PPDU is received, and when the second parameter set timerexpires, terminating the application of the second parameter set. 18.The method of claim 17, wherein the setting of the second parameter settimer comprises setting the second parameter set timer when theimmediate response reception ends.
 19. The method of claim 17, whereinthe setting of the second parameter set timer comprises setting thesecond parameter set timer for an access category of an MPDU for whichthe immediate response is received.
 20. The method of claim 17, whereinthe setting of the second parameter set timer determines when to set thesecond parameter set timer based on a type of responding requested bythe MPDU included in the trigger-based PPDU.